This invention relates to a method of carrying out crystal growth of a compound semiconductor and, in particular, to a method of controlling selective crystal growth.
In order to manufacture a semiconductor device, use is generally made of so-called selective crystal growth in which crystal growth of a compound semiconductor is restricted only to a desired area of a substrate.
There have been known conventional methods of carrying out such selective growth by the use of a thin film of SiO.sub.2 or the like. According to those methods, the SiO.sub.2 film is formed on a surface of a substrate and selectively removed to expose the substrate at an area on which crystal growth of the compound semiconductor has to be carried out. Subsequently, crystal growth is carried out to grow the compound semiconductor on the substrate only on the exposed area. As the methods of the type described, a method using MBE is disclosed in Applied Physics Letters, Vol. 51 (1987), pp. 1512-1514 and another method using MOCVD is disclosed in Journal of Crystal Growth, Vol. 77 (1986), pp. 303-309.
In order to bury the compound semiconductor selectively grown by the use of the SiO.sub.2 film as described above, crystal growth of another compound semiconductor is made on the side surface of the compound semiconductor under two-dimensional control. Such a technique is disclosed in Applied Physics Letters, Vol. 57 (1990), pp. 1209-1211. According to this technique, the compound semiconductor is grown on a (111)B substrate by a MOCVD method. Another compound semiconductor is grown only on the side surface of the compound semiconductor previously grown by selective crystal growth.
However, in the method of carrying out selective growth by the use of the SiO.sub.2 film, it is necessary to accelerate decomposition and evaporation on the SiO.sub.2 film in order to inhibit crystal growth on the SiO.sub.2 film. This means that crystal growth must be carried out at a high temperature. Specifically, it is reported in the above-referenced papers that the growth must be carried out at a temperature not lower than 700.degree. C. in the MBE method and at a temperature not lower than 620.degree. C. in the MOCVD method. The crystal growth at such a high temperature often brings about diffusion of impurities for controlling a conduction type.
In addition, in the method of carrying out selective growth by the use of the SiO.sub.2 film, the crystal growth can be controlled only in a one-dimensional direction (perpendicular to the substrate).
In the method of burying the side surface of the compound semiconductor selectively grown on the (111)B substrate, another compound semiconductor later grown is formed on the SiO.sub.2 film. Accordingly, it is impossible to manufacture a buried structure completely buried by the semiconductor.
Furthermore, the MOCVD method uses arsine which is highly toxic.